Gale, S, Farrington, L, Bergström, P, Suikkanen, M, Boldrini, N, Rubino, M, Coli, N, Naude, S, Stopka, CJ & Preston, C 2020, 'Monitoring applications for safe mining practices: case studies of sub-bench 
scale failures in hard rock and coal open cut mines', in PM Dight (ed.), Slope Stability 2020: Proceedings of the 2020 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering, Australian Centre for Geomechanics, Perth, pp. 1563-1576, https://doi.org/10.36487/ACG_repo/2025_108
(https://papers.acg.uwa.edu.au/p/2025_108_Boldrini/)
Abstract: In the modern mining industry, mining companies are coming under increasing pressure to improve the performance and efficiency of their operations. Special attention has been given not only to potential large-scale movements, but also to local-scale instabilities within active mining areas which can be difficult to manage. Sub-bench scale failures pose a threat to miners and machinery due to the closeness to working areas and identifying these areas before failure helps minimise production interruption. For this reason, a comprehensive slope monitoring program should be introduced and required in every geotechnical risk assessment plan. This paper presents three case studies, an apatite mine and a nickel-PGE-copper mine located in Finland and an open cut coal mine situated in Queensland. The nickel-PGE-copper mine is characterised mostly by bench scale failures: structurally controlled wedge failures and tight healed structures. Furthermore, some of the 90° benches, which are close to the only active ramp that permits transit, are full of waste material. In the apatite mine, most of the events can be classified as local bench to sub-bench failures that take place along the major joint planes with limited deformation before failure. Finally, the open cut coal mine, located in the Bowen Basin, has had a series of large highwall failures caused by tectonically disturbed silt/mudstone horizon located above the target coal seam which form large nonuniform blocks that can drop out posing a risk to operations below. A new technological solution of IDS GeoRadar, Hydra-X, which allows for sub-bench monitoring, was deployed to understand the failure mechanisms and to identify instability areas. In the three case studies, the equipment was able to capture sub-millimetre displacements where no visible deformation was visible on the face. These three case studies describe and provide examples of complex modern mining operations where local failures have created the need to revaluate the existing slope monitoring program to have an increasing knowledge of the stability problems and to support geotechnical engineers in managing the risk.

Keywords: slope monitoring, sub-bench failures, working areas, geotechnical risk assessment plan, Hydra-X